The present invention relates generally to improvements in vehicle safety belt systems, and it relates more particularly to an improved inertia actuated automatic locking vehicle safety belt retraction reel.
In emergency locking retractors of the type used with a vehicle safety belts and designed to prevent extraction or withdrawal of the belt under emergency conditions, such as a collision, overturning and sudden stop, it is a known practice to lock the belt against extraction in response to the inertial force of rotation that is produced by the safety belt as it is suddenly unreeled in such an emergency, as a result of the sudden forward movement of the vehicle seat occupant's body. When the acceleration sensing capacity of a retractor of this kind is of such a range that a rather low acceleration, such as 0.3G, may be sensed, the inertia unit is activated even when the passenger suddenly, rapidly, withdraws the belt with the intention of applying the belt. With actuation of the inertia unit, the belt is locked, and the passenger may occasionally dispense with the application of the safety belt. In a retractor in which the vehicle acceleration and deceleration produced at the time of collision or other accident is sensed for locking the belt, when the sensing unit is installed in the retractor itself and must have a wide sensing range, such as 0.3 to 1.0G, the retractor is excessive in size and occupies too much space in the vehicle body. When the sensing unit of this type is installed separately from the retractor, it is necessary to provide an electrical network within the vehicle so that, in some kinds of vehicles, it is impossible to provide the vehicle with the retractor device.
The present invention contemplates the provision of an automatic locking retraction reel in which an acceleration in the range, for example, from 0.3 to 1.0G which requires a higher sensing capacity is sensed by a pendulum unit to effect the locking of the safety belt, and an acceleration beyond, for example, 0.7G is sensed by an inertia unit for correspondingly locking the belt. Therefore, when the passenger desires to apply the safety belt, it can be freely extracted without locking even at a very high withdrawal speed. At a lower range of acceleration as produced, for instance, in the case of a sudden stop or tilt of the vehicle, the belt is locked by operation of the pendulum sensing unit. At a very high rate of acceleration as produced, for instance, in the case of a collision, the inertia unit is actuated due to the sudden movement of the seat occupant's body and the resulting extraction of the safety belt, so that the belt is automatically locked. While the retractor of the present invention is equipped with two sensing units, namely, the pendulum sensing unit and the inertia sensing unit, almost all of the component parts are used in common for the two sensing units and other units of the retractor, so that the production cost can be low, despite the use of the dual safety system. In addition, the retractor can be mounted conveniently in any vehicle because electrical devices and wiring are obviated.